This invention relates to apparatus for supporting a flexible member on a layer of a gaseous medium. More particularly, this invention relates to apparatus for supporting and tentering on a layer of a gaseous medium, a copy sheet having unfixed toner images on one or both sides thereof which is moved between a moving photoconductive member and a fuser.
It is often desirable to support a flexible member moved along a path of travel into or between work stations without physically contacting it. Thus, in electrophotographic copiers, copy sheets carrying unfixed toner images on one or both sides are moved between a photoconductive member and a fusing station at which the unfixed images are fixed to the sheet. If the unfixed toner images are contacted with rollers or conveyors before they are fixed to the copy sheet, the likelihood exists of disturbing the images on the sheet and thereby degrading image quality. It is therefore desirable to support the copy sheet by other than mechanical means. Although copy sheet support techniques utilizing a gaseous medium have been proposed for supporting copy sheets between a photoconductive member or developing means and a fixing station, such techniques have not been successful in handling copy sheets of different weights and sizes where the copy sheet carrying unfused toner images is to be fed into a roller fuser. In such fusers, point of entry of the leading edge of the copy sheet into the fuser roller nip is critical in order to minimize dynamic distortions of the copy sheet which cause image defects.
It is thus desirable that apparatus be provided for supporting copy sheets moved between a photoconductive member and a fixing station in such manner that unfixed toner images on the sheets are not disturbed. The apparatus should be capable of handling copy sheets of different sizes and weights without the necessity of readjusting the apparatus. It is also desirable that the support apparatus be able to deliver the leading edge of the copy sheet in a controlled manner to a precise entry region of a fuser roller nip in order to prevent image defects being produced during the fusing process. To this end the copy sheet should be maintained essentially flat during its movement and be tentered to avoid wrinkles or creases forming before entry into the roller fuser. The support apparatus should be compact, economical, and easily serviced.